Answer:
Nobody knows they are doing bad things. They do what is most appealing to them. Not necessarily rational, but the person's primary interest. So, it depends on the person. "Bad" is completely subjective, so it depends on the situation and the parties involved. As a general rule, however, there are seven common reasons.
Hurt.
Fear.
Insecurity.
Inclusion.
Exclusion.
Guilt.
Shame.